Ocean Nitrogen Rising

Changes in the ratio of nitrate to phosphorus in the oceans off the coasts of Korea and Japan may influence marine ecology and the makeup of marine plants, according to researchers from Korea and the U.S. Rising nitrate levels are caused by atmospheric and river pollutants.

“Normally in a marine environment nitrate is the limiting factor, but increased nitrate in the ocean can spur growth and create a situation where phosphorus becomes the nutrient in short supply,” said Raymond G. Najjar, professor of oceanography at Penn State University. “This change in nutrients could favour organisms that are better suited for high nitrate and low phosphorus.”

According to the researchers, the effects of anthropogenic nitrate pollution from the air have been shown to be significant in local lakes, streams and estuaries in Norway, Sweden and the U.S. But this is the first time evidence has been seen in of an increase in nitrate in a large, deep, body of water.

The area studied included the Yellow Sea, the Sea of Japan and the East China Sea. The researchers found that the phosphorus levels in the ocean water remained the same through time. The abundance of nitrogen relative to phosphorus, though, has increased significantly since 1980, the researchers report in today’s (September 23) online edition of Science Express.

The Yellow Sea is one of the largest shallow areas of continental shelf in the world and is home to a diverse range of species including dugongs, grey whales, turtles and rich fish life.

Further Reading:
Increasing N Abundance in the Northwestern Pacific Ocean Due to Atmospheric Nitrogen Deposition, Science DOI: 10.1126/science.1206583
The other source of nitrate into the oceans is from runoff from industry and agriculture that reaches the seas via rivers. In most cases, this nitrogen is quickly diluted.